a. Field of the Invention
The present invention relates to method and apparatus for manufacturing wrapped yarns and relates, more particularly, to methods and apparatus for manufacturing wrapped yarns formed of a central core of roving or the like drafted yarn which is helically wrapped with a binder strand.
In the following specification, the terms "yarn" and "strand" are used in a general sense to apply to all kinds of strand material, either textile or otherwise, and the terms "package" and "spool" are intended to mean the product of a winding machine, whatever its form. The term "balloon" refers to the path defined by the rotating portion of a rotated advancing strand irrespective of the shape or diameter of said path, and sometimes refers to the yarn in said path, according to the context in which the term is employed.
b. Problem of the Invention
In the art of manufacturing wrapped yarn in which a cover or binder strand is helically wrapped around a drafted core strand or strands to form such wrapped yarn, a tendency for loose fibers escaping from the drafting system and other airborne waste to collect on the binder strand can be observed. When such waste does collect on the binder strand it eventually forms enlarged areas on the binder strand which can ultimately become wrapped into the final yarn product, thereby reducing the quality of that yarn and product. Alternatively, such collections or airborne waste on the binder strand contribute to high tensions in the binder strand especially in the area where the balloon is formed and lead to eventual breakage of the binder strands of the wrapped yarn.
It is, therefore, a primary object of the invention to provide an improved method and apparatus for obtaining high quality wrapped yarns while substantially reducing or eliminating loss in product quality due to the ballooning binder strand picking up airborne fiber waste thereon while being wrapped around a core strand.
Most wrapped or covered yarns are formed by directing a core strand through a hollow spindle as a ballooning binder strand is being withdrawn from a rotating package on the spindle and is being wrapped around the core strand. In some instances it is particularly desirable, if not necessary, that the wrapping of the core strand be effected closely adjacent to the entrance of the hollow spindle in which the core strand is being directed since the hollow spindle then aids in better controlling wrapping of the binder strand about the core strand and in guiding the core strand during the wrapping process. This is particularly the case in the formation of a wrapped yarn having a core strand formed of drafted, generally untwisted staple fibers about which a binder strand is being wrapped.
Typical apparatuses for forming wrapped yarns are disclosed in U.S. Pat. Nos. 3,328,946; 3,831,369, and 4,018,042.
As is well known, substantial amounts of fiber waste in the form of fine airborne waste fibers, or, in the parlance of the textile industry, "fly", are generated by textile machines which process staple fibers and form textile strands therefrom. It has been observed that a substantial amount of this fly is actually derived from the roving being drafted, and this, a substantial amount of the fly proximate any given wrapping station is probably generated by the roving or core strand being processed at that station. It can be appreciated, therefore, that substantial amounts of fiber waste generally are present in the ambient air adjacent machines for wrapping binder strands about core strands formed of untwisted staple fibers. It is also well known that, during the formation of a wrapped yarn in the manner indicated in the above, the binder strand inherently balloons outwardly its path of travel from the package to the core strand being wrapped, i.e., a rapidly rotating ballooning binder strand is present between each binder strand package and the end of the corresponding spindle adjacent which the binder strand is being wrapped around the rest of core strand. Such rapidly rotating ballooning binder strand attracts fiber waste from the ambient air during rotation thereof and while some of the picked up fiber waste is likely thrown off the ballooning binder strand by centrifugal force, much of the fiber waste adheres to the rotating ballooning strand.
Heretofore, in many instances, the fiber waste picked up by the rotating ballooning binder strands stays adhered thereto and grows in size until substantial masses or wads of fiber waste, i.e., so called "flags", are formed on the binder strands. Frequently, the flags are continuously "skinned" back along the binder strand by centrifugal forces and collect in the ballooning area of the binder strand until the ballooning binder strand eventually breaks. Alternatively, some of such wads of accumulated fiber waste would eventually cling to the binder strand and no longer be "skinned" back but, rather, would be carried along with the binder strand and wrapped about the core strand, thus resulting in objectionable slubs or enlarged places in the wrapped yarn being formed. Such defects, of course, reduce the quality of the wrapped yarn. Also, such defects would often cause breakage of the wrapped yarn in subsequent processes such as during passage of the wrapped yarn through the yarn guides and needles of knitting machinery or through stop motions, heddles and reeds of weaving machinery. Further, in rewinding operations, where the wrapped yarn is rewound in cones, it is usual to advance the yarn through a slub catcher during the rewinding operation where the detected slubs are cut out of the yarn then being retied and the rewinding operation continued. Obviously, if the wrapped yarn possesses numerous slubs or flags of objectionable size, the rewinding equipment is going to result in reduced production as it is stopped to tend to removal of the flags. Further, the rewound yarn will have a knot therein where each flag has been cut out thus reducing the quality of the wrapped yarn.
It has been determined that an important cause of end-down conditions in wrapping machines of the character under discussion is the fact that picked-up fiber waste accumulated on the ballooning binder strand would increase to such a mass and weight that centrifugal forces acting thereon would increase beyond the tensile strength of the binder strand. Such end-down condition is a particularly serious problem with the wrapped yarns in accordance with the afore-mentioned commonly assigned U.S. Pat. No. 3,831,369 because, when the binder strand breaks, wrapping about the drafted core strand ceases, the core strand cannot then sustain its own integrity and moves away from the delivery rolls toward the hollow spindle in the form of an uncontrolled mass of open fibers. Such uncontrolled fibers quickly disseminate in the air currents and often times will settle on other yarns being processed on the machine, thus degrading the quality of these other yarns or causing them to break and thereby aggravate the ends-down problem. A further problem arises when the binder strand ruptures and the core strand, rather than breaking immediately, continues to issue from the drafting system and becomes caught within the rapidly rotating spindle supporting the supply of binder strand. With the core yarn so trapped it eventually billows out of the top of the spindle either as a balloon still held at one of its ends by the spindle and still issuing out of the drafting system, or the core strand may break near the drafting system and the loose end held in the rotating spindle can flail about. In either event, the core yarn can then entangle with adjacent core strands, resulting in the break-out of these adjacent core strands in a domino effect.
c. Discussion of Prior Art
In commonly assigned U.S. Pat. No. 3,899,867 method and apparatus are disclosed and claimed for mechanically intermittently and partially collapsing the normal path of travel of the ballooning binder strand so as to impart a delaying movement thereto with consequential vibration of the balloon to cause most fiber waste picked up by the binder strand to be cast off by the same. While the method and apparatus of the -867 patent are effective for the objects just mentioned, it is always desirable to avoid any mechanical contact with a rapidly revolving yarn balloon. Furthermore, it has been found that in practice, particularly where the core strand is comprised of fibers of very short staple the amount of fly in the ambient air may be so great that it is advantageous to completely isolate the zone wherein the binder strand is ballooning to further insure that the binder strand is substantially free of any collections of fiber waste.
In a more recent addition to the prior art, U.S. Pat. No. 4,018,042, which is specifically concerned with a special combination of wrapped yarn properties as well as with the peculiar processing conditions needed to produce them, there is incidentally shown a balloon limiting cylinder approximately coextensive in length with the binder strand package supported on a driven hollow inner spindle, all rotating as an integral unit, and in an alternative embodiment a hollow package held within an external cylindrical container fixed on its bottom wall to the spindle and its upper wall projecting flange-like inwardly to a point spaced from the hollow spindle periphery and below the upper end of the spindle. In such arrangements, a binder balloon of considerable magnitude would necessarily develop in the open region outside the confines of these enclosures and especially in the immediate proximity of the entrance to the spindle bore, and thus to the wrapping zone itself. Consequently, the problems caused by the entrainment of airborne waste by the binder balloon are neither addressed nor resolved by the system of this patent.